Tag: black rain

Wet scrubber systems using seawater or freshwater uses big amount of water to dissolve SOx included in the exhaust gas from marine diesel engines. Most of the sprayed water goes down to the drain, but some of the carry-over condensates by the exhaust gas flow and condensates created after the outlet of scrubber units may generate water drops falling on the ship.

Various efforts have been made to remove the water drops falling on the ship: large heater, induction fan, and mist eliminator. Large heaters heat-up the flow to evaporate condensates but requires electric power. Induction fans would be a good choice but the entire scrubber system depends on the fan, which may add some large back pressure to the exhaust gas pipe system. Mist eliminator uses static filter so called as ‘chevron mist ‘, which collects condensates and drains. Problem with the mist eliminators are filter blockage and large size.

Manufacturers of ‘Chevron’ type mist eliminators recommend that the flow speed when passing through the filter units would be limited to be 2.5m/s (as slow as possible, of course). This is a tough requirements for applications like scrubber systems.

Exhaust gas flow speed is around 25~30m3/s within exhaust gas pipes.

To reduce the speed, cross section area should be increased by almost 10 times of exhaust gas pipes.

When the filter unit is installed horizontally, draining of collected condensates becomes an issue unless the cross section diameter is increased more than 3 times of existing exhaust gas pipes…this is why most of the scrubber manufacturers in the market should have a huge diameter in the demister section.

Through the past project experience, STI has gains enough experience to deal with the condensates. STI provides small-scale and blockage-tolerant demister system together with its SOx scrubber system.